Android scroller Simple usage

The Scroller class in Android is a helper class to implement view smooth scrolling. Usually used in custom view, a private member Mscroller = new Scroller (context) is defined in view. Setting the Mscroller scrolling position does not cause the view to scroll, usually using Mscroller to record/calculate the position of the view scroll, and then rewrite the view's Computescroll () to complete the actual scrolling.

Related APIs are described below
Java code

2. Mscroller.getcurrx () //Get position of mscroller current horizontal scroll
4. Mscroller.getcurry () //Get position of mscroller current vertical scroll
6. MSCROLLER.GETFINALX () //Get Mscroller final stop horizontal position
8. Mscroller.getfinaly () //Get the vertical position of the Mscroller final stop
10. MSCROLLER.SETFINALX (int newx) //Set the horizontal position of the Mscroller final stop, no animation effect, jump directly to the target position
12. Mscroller.setfinaly (int newy) //Set the vertical position of the Mscroller final stop, no animation effect, jump directly to the target position
16. Scroll, StartX, starty to start scrolling position, dx,dy for scrolling offset, duration for time to complete scrolling
18. Mscroller.startscroll (int startX, int starty, int dx, int dy) //Use default finish time 250ms /c3>
20. Mscroller.startscroll (int startX, int starty, int dx, int dy, int duration)
24. Mscroller.computescrolloffset () ///return value boolean,true indicates that scrolling is not complete, false to indicate that scrolling is complete.  This is a very important method, usually placed in View.computescroll (), to determine whether scrolling is over or not.

For example, to customize a customview, use Scroller to implement scrolling:

Java code

2. Import Android.content.Context;
4. Import Android.util.AttributeSet;
6. Import Android.util.Log;
8. Import Android.view.View;
10. Import Android.widget.LinearLayout;
12. Import Android.widget.Scroller;
16. Public class CustomView extends LinearLayout {
20. private static final String TAG = "Scroller";
24. private Scroller Mscroller;
28. Public CustomView (context context, AttributeSet attrs) {
30. Super (context, attrs);
32. Mscroller = New Scroller (context);
34. }
38. //Call this method to scroll to the target location
40. public void Smoothscrollto (int fx, int fy) {
42. int dx = FX-MSCROLLER.GETFINALX ();
44. int dy = fy-mscroller.getfinaly ();
46. Smoothscrollby (dx, dy);
48. }
52. //Call this method to set the relative offset of the scrolling
54. public void Smoothscrollby (int dx, int dy) {
58. //Set the scroll offset of the Mscroller
60. Mscroller.startscroll (Mscroller.getfinalx (), mscroller.getfinaly (), DX, DY);
62. Invalidate (); //Must call Invalidate () here to ensure that computescroll () will be called, otherwise it will not necessarily refresh the interface, see Scrolling effect
64. }
68. @Override
70. public void Computescroll () {
74. //To determine if the Mscroller scroll is complete first
76. if (Mscroller.computescrolloffset ()) {
80. //This calls the view's Scrollto () to complete the actual scrolling
82. ScrollTo (Mscroller.getcurrx (), Mscroller.getcurry ());
86. //You must call this method, or you may not see the scrolling effect
88. Postinvalidate ();
90. }
92. Super.computescroll ();
94. }
96. }

• Scrollerdemo.rar (322.3 KB)

Android scroller Simple usage